— 321 — 



ante mecliuiii sitis; valvulae inaequales, sinistra major magis 

 convexa, postice leviter liiantes, teiinissimne, subniembranaceae, 

 albido-tiavescentes, subtiliter radiatim striatae, epidermide tenui, 

 fibrosa, saepius arenulis obtecta, intus nitidissimae, iridescentes, 

 cardine edentulo sed ossiculo libero sat magno quadrato in- 

 structo. — Long. 27 Mm. 



Lyousia norvegica (Mya) Cheiiiiiitz vol. X p. 345 T. 170F. 1647.48. 

 — (Aiiatina) Sow. Gen F. 2. — (L.) Soav Concli. Man. F. 491, 

 492. — Forbes et Hanley I p 214 T 7, F. 6, 7.— Sow. 111. Ind. 

 T. 2, F. 4. - Jeffreys Br. Concli. III p 29 T. 48, F. 2. - Lo- 

 card Cat p. 392. - Sars Norv. p. 81. 

 Mya nitiila Fabr. Skr. nat. selsk. IV 1798 T. 10, F. 10. 

 Amphidesma corbuloides Lamarck VI p. 85 



Amphidesma pellucida Brown Mem. Wern. Soc. II p. 505 T. 24F. 1. 

 Mya striata Moutagu Linn. Trans. XI p. 188 T. 1, F. 13. 

 Myatella striata Brown III. Conch. (2) p. 111 T. 40, F. 26. 27. 

 Hab. ab insulis Lofotensibus usque ad mare Mediterraneum. 



2. Lyonsia formosa Jeffreys. T. ovata, aequivalvis, 

 margaritacea, tenuis, subtranslucens , argenteo-alba, tuberculis 

 minutis seriatim longitudinaliter disi^ositis coiifertim sculpta pli- 

 cisque diagonalibus, interna inajore, cariniformi, tiexuosis munita ; 

 margo anterior rotundatus, inferior postice leviter sinuatus, 

 posterior subtruncatus, superior convexus ; umboiies triangulares, 

 antrorsum inclinati. Cardo lamina elongata, crassa; ossiculum 

 margaritaceum, cordiforme, in cartilagine luteo-fusco inclusum; 

 fovea ovalis, mar.iiinibus incrassatis; latus internum politum, 

 iridescens, impressionibus distinctis — Long. 13, alt. 8 Mm. 



Lyonsia formosa Jeffreys Pr. Z. S. 1881 p. 930 T. 70, F. 1. — 

 Locard Cat. p. 393. 

 Hab. in abyssis maris atlantici, nec non in sinu Caribaeo. 



3. Lyonsia argentea Jeffreys. T. ovato-triquetra, 

 solidula, opaca, lutescenti-albida, tuberculis subtilissimis ubique 

 armata, in valv. dextra lineis nonnullis radiantibus, in parte 

 posteriore sinistrae costa radiante sculpta, marginibus antice 

 leviter curvatis, ad oras fibrosis; umbones triangulares , leviter 

 incurvati; lamelLa cardinalis crassa; latus intemum argenteum. 

 L. cca. 16 Mm. 



Lyonsia argentea Jeffreys Pr. Z. S. 1881 p 930 T. 70, F. 2. 

 Hab. in Oceani atlantici abyssis nec non prope Panormum. 



4. Lyonsia arenosa Moller. T. subtumida, inaequi- 

 valvis, valvula sinistra inajore et forma a dextra leviter discre- 

 pante, oblongo-ovata, extremitate antica longiore et latiore ad 

 apicem truncata, postica brevi obtuse rotundata non rostrata, 

 margine ventrali aequaliter arcuato, dorsali antico subrecto, 

 horizontali, margini ventrali subparallelo, postico leviter con- 

 cavo, umbonibus tumidulis incurvatis, pone medium sitis, lunula 

 conspicua depressa. Valvulae tenues et fragiles, albido-cinereae, 

 radiatim striolatae, striis regularibus et distantibus, eminentiam 

 diagonalem ab uinbonibus ad angulum inf. extr. anticae exten- 



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